IL-6-Dependent PGE2 Secretion by Mesenchymal Stem Cells Inhibits Local Inflammation in Experimental Arthritis

BACKGROUND: Based on their capacity to suppress immune responses, multipotent mesenchymal stromal cells (MSC) are intensively studied for various clinical applications. Although it has been shown in vitro that the immunomodulatory effect of MSCs mainly occurs through the secretion of soluble mediators, the mechanism is still not completely understood. The aim of the present study was to better understand the mechanisms underlying the suppressive effect of MSCs in vivo, using cells isolated from mice deficient in the production of inducible nitric oxide synthase (iNOS) or interleukin (IL)-6 in the murine model of collagen-induced arthritis. PRINCIPAL FINDINGS: In the present study, we show that primary murine MSCs from various strains of mice or isolated from mice deficient for iNOS or IL-6 exhibit different immunosuppressive potential. The immunomodulatory function of MSCs was mainly attributed to IL-6-dependent secretion of prostaglandin E2 (PGE2) with a minor role for NO. To address the role of these molecules in vivo, we used the collagen-induced arthritis as an experimental model of immune-mediated disorder. MSCs effectively inhibited collagen-induced inflammation during a narrow therapeutic window. In contrast to wild type MSCs, IL-6-deficient MSCs and to a lesser extent iNOS-deficient MSCs were not able to reduce the clinical signs of arthritis. Finally, we show that, independently of NO or IL-6 secretion or Treg cell induction, MSCs modulate the host response by inducing a switch to a Th2 immune response. SIGNIFICANCE: Our data indicate that mscs mediate their immunosuppressive effect via two modes of action: locally, they reduce inflammation through the secretion of anti-proliferative mediators, such as NO and mainly PGE2, and systemically they switch the host response from a Th1/Th17 towards a Th2 immune profile

Role of vascular channels as a novel mechanism for subchondral bone damage at cruciate ligament entheses in osteoarthritis and inflammatory arthritis.

Objectives: The purpose of this work was to test whether normal peri-entheseal vascular anatomy at anterior and posterior cruciate ligaments (ACL and PCL) was associated with distribution of peri-entheseal bone erosion/bone marrow lesions (BMLs) in inflammatory arthritis (IA) and osteoarthritis (OA). Methods: Normal microanatomy was defined histologically in mice and by 3 T MRI and histology in 21 cadaveric knees. MRI of 89 patients from the Osteoarthritis Initiative and 27 patients with IA was evaluated for BMLs at ACL and PCL entheses. Antigen-induced arthritis (AIA) in mice was evaluated to ascertain whether putative peri-entheseal vascular regions influenced osteitis and bone erosion. Results Vascular channels penetrating cortical bone were identified in knees of non-arthritic mice adjacent to the cruciate ligaments. On MRI of normal cadavers, vascular channels adjacent to the ACL (64% of cases) and PCL (71%) entheses were observed. Histology of 10 macroscopically normal cadaveric specimens confirmed the location of vascular channels and associated subclinical changes including subchondral bone damage (80% of cases) and micro-cyst formation (50%). In the AIA model, vascular channels clearly provided a site for inflammatory tissue entry and osteoclast activation. MRI showed BMLs in the same topographic locations in both patients with early OA (41% ACL, 59% PCL) and IA (44%, 33%). Conclusion: The findings show that normal ACL and PCL entheses have immediately adjacent vascular channels which are common sites of subtle bone marrow pathology in non-arthritic joints. These channels appear to be key determinants in bone damage in inflammatory and degenerative arthritis

Role of the IL-1 Pathway in Dopaminergic Neurodegeneration and Decreased Voluntary Movement

Interleukin-1 (IL-1), a proinflammatory cytokine synthesized and released by activated microglia, can cause dopaminergic neurodegeneration leading to Parkinsons disease (PD). However, it is uncertain whether IL-1 can act directly, or by exacerbating the harmful actions of other brain insults. To ascertain the role of the IL-1 pathway on dopaminergic neurodegeneration and motor skills during aging, we compared mice with impaired [caspase-1 knockout (casp1(-/-))] or overactivated IL-1 activity [IL-1 receptor antagonist knockout (IL-1ra(-/-))] to wild-type (wt) mice at young and middle age. Their motor skills were evaluated by the open-field and rotarod tests, and quantification of their dopamine neurons and activated microglia within the substantia nigra were performed by immunohistochemistry. IL-1ra(-/-) mice showed an age-related decline in motor skills, a reduced number of dopamine neurons, and an increase in activated microglia when compared to wt or casp1(-/-) mice. Casp1(-/-) mice had similar changes in motor skills and dopamine neurons, but fewer activated microglia cells than wt mice. Our results suggest that the overactivated IL-1 pathway occurring in IL-1ra(-/-) mice in the absence of inflammatory interventions (e.g., intracerebral injections performed in animal models of PD) increased activated microglia, decreased the number of dopaminergic neurons, and reduced their motor skills. Decreased IL-1 activity in casp1(-/-) mice did not yield clear protective effects when compared with wt mice. In summary, in the absence of overt brain insults, chronic activation of the IL-1 pathway may promote pathological aspects of PD per se, but its impairment does not appear to yield advantages over wt mice.Funding Agencies|John Curtin School of Medical Research, The Australian National University</p

Low CD4/CD8 T-Cell Ratio Associated with Inflammatory Arthropathy in Human T-Cell Leukemia Virus Type I Tax Transgenic Mice

Human T-cell leukemia virus type I (HTLV-1) can cause an aggressive malignancy known as adult T-cell leukemia/lymphoma (ATL) as well as inflammatory diseases such as HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). A transgenic mouse that expresses HTLV-1 Tax also develops T-cell leukemia/lymphoma and an inflammatory arthropathy that resembles rheumatoid arthritis. The aim of this study was to identify the primary T-cell subsets involved in the development of arthropathy in Tax transgenic mice. mRNA was strong in the spleen and joints of arthropathic mice, with a 40-fold increase compared with healthy transgenic mice.Our findings reveal that Tax transgenic mice develop rheumatoid-like arthritis with proliferating synovial cells in the joints; however, the proportion of different splenic T-cell subsets in these mice was completely different from other commonly used animal models of rheumatoid arthritis. The crucial T-cell subsets in arthropathic Tax transgenic mice appear to resemble those in HAM/TSP patients rather than those in rheumatoid arthritis patients

Evaluation of TNF-alpha and IL-1 blockade in collagen-induced arthritis and comparison with combined anti-TNF-alpha/anti-CD4 therapy.

We have evaluated the effects of anti-TNF-alpha, anti-IL-1, and combined anti-TNF-alpha/anti-CD4 therapy in collagen-induced arthritis. Blockade of TNF-alpha or IL-1 before disease onset delayed, but did not prevent, the induction of arthritis. When treatment was initiated after onset of arthritis, anti-TNF-alpha, anti-IL-1beta, and anti-IL-1R (which blocks IL-1alpha and IL-1beta) were all found to be effective in reducing the severity of arthritis, with anti-IL-1R and anti-IL-1beta showing greater efficacy than anti-TNF-alpha. Anti-IL-1beta was equally as effective as anti-IL-1R, indicating that IL-1beta plays a more prominent role than IL-1alpha in collagen-induced arthritis. An additive effect was observed between anti-TNF-alpha and anti-IL-1R in the prevention of joint erosion and in normalization of the levels of serum amyloid P. Combined anti-TNF-alpha/anti-CD4 therapy also caused normalization of serum amyloid P levels. The therapeutic effect of anti-TNF-alpha plus anti-CD4 was comparable to that of anti-TNF-alpha plus anti-IL-1R, suggesting that combined anti-TNF-alpha/anti-CD4 therapy prevents both TNF-alpha- and IL-1-mediated pathology. Anti-TNF-alpha treatment reduced IL-1beta expression in the joint and, conversely, anti-IL-1beta treatment reduced TNF-alpha expression. Combined anti-TNF-alpha/anti-CD4 treatment almost completely blocked the expression of IL-1beta, thereby confirming the ability of this form of combination therapy to prevent IL-1ss-mediated pathology

Remission of collagen-induced arthritis is associated with high levels of transforming growth factor-beta expression in the joint.

Immunization of genetically susceptible strains of mice with heterologous type II collagen leads to the induction of a self-limiting polyarthritis that begins to subside around 10 days after onset of clinical disease. The aims of this study were to compare pro- and anti-inflammatory cytokine expression in the joints during the course of arthritis in order to identify cytokines involved in spontaneous remission of arthritis. DBA/1 mice were immunized with type II collagen and an immunohistochemical analysis of expression of proinflammatory cytokines [tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta and IL-6] and anti-inflammatory cytokines [IL-10, IL-1ra, transforming growth factor (TGF)-beta1, TGF-beta2 and TGF-beta3] in joints was carried out over the course of the disease. Both pro- and anti-inflammatory cytokines were found to be expressed in early arthritis. However, around 10 days after onset of arthritis, the level of expression of proinflammatory cytokines declined while the level of expression of anti-inflammatory cytokines, particularly TGF-beta1 and TGF-beta2, increased. Surprisingly, TNF-alpha continued to be expressed at low levels during the period of disease remission (30 days after onset). Blockade of TNF-alpha during the period of disease remission had no effect on TGF-beta expression. This study confirms that the level of inflammation in arthritis correlates strongly with the balance of pro- and anti-inflammatory cytokine expression in the joints. Of the anti-inflammatory cytokines studied, TGF-beta1 and TGF-beta2 predominate during the time of disease remission, suggesting that these cytokines are involved in regulating disease activity

An anti-inflammatory role for interleukin-11 in established murine collagen-induced arthritis.

Interleukin-11 (IL-11) is a cytokine belonging to the IL-6 family which has both pro- and anti-inflammatory potential. Like IL-6 it can diminish tumour necrosis factor-alpha and IL-1 production, and augment immunoglobulin synthesis. We have explored the immunomodulatory effects of IL-11 treatment in mice in a model of inflammatory autoimmune joint disease, collagen-induced arthritis (CIA). Recombinant human IL-11 was administered at various doses to DBA/1 mice after the onset of CIA. IL-11 treatment caused a significant reduction in the clinical severity of established CIA, which was associated with protection from joint damage, as assessed by histology. Although there was a suggestion at high doses of IL-11 that the anticollagen type II (CII) response may have been augmented, there was no statistically significant effect of IL-11 treatment on anti-CII antibody levels. Similarly, the acute-phase reactant serum amyloid P was only elevated in mice receiving very high doses (50-100 microgram/day) of IL-11. Endogenous IL-11 was abundantly produced in synovial membrane cultures derived from CII-immunized mice with active disease, suggesting that, as in rheumatoid arthritis, this cytokine is spontaneously produced in the inflammatory response in CIA. The results presented here demonstrate an anti-arthritic immunoregulatory role for IL-11 in murine CIA, and suggest that IL-11 is a candidate therapeutic molecule for human inflammatory arthritic diseases

An anti-inflammatory role for interleukin-11 in established murine collagen-induced arthritis.

Interleukin-11 (IL-11) is a cytokine belonging to the IL-6 family which has both pro- and anti-inflammatory potential. Like IL-6 it can diminish tumour necrosis factor-alpha and IL-1 production, and augment immunoglobulin synthesis. We have explored the immunomodulatory effects of IL-11 treatment in mice in a model of inflammatory autoimmune joint disease, collagen-induced arthritis (CIA). Recombinant human IL-11 was administered at various doses to DBA/1 mice after the onset of CIA. IL-11 treatment caused a significant reduction in the clinical severity of established CIA, which was associated with protection from joint damage, as assessed by histology. Although there was a suggestion at high doses of IL-11 that the anticollagen type II (CII) response may have been augmented, there was no statistically significant effect of IL-11 treatment on anti-CII antibody levels. Similarly, the acute-phase reactant serum amyloid P was only elevated in mice receiving very high doses (50-100 microgram/day) of IL-11. Endogenous IL-11 was abundantly produced in synovial membrane cultures derived from CII-immunized mice with active disease, suggesting that, as in rheumatoid arthritis, this cytokine is spontaneously produced in the inflammatory response in CIA. The results presented here demonstrate an anti-arthritic immunoregulatory role for IL-11 in murine CIA, and suggest that IL-11 is a candidate therapeutic molecule for human inflammatory arthritic diseases